journal: add ability to browse journals of running OS containers

This adds the new library call sd_journal_open_container() and a new
"-M" switch to journalctl. Particular care is taken that journalctl's
"-b" switch resolves to the current boot ID of the container, not the
host.

3 files changed, 70 insertions, 18 deletions

diff --git a/src/journal/journalctl.c b/src/journal/journalctl.c
index f74dde9c48..5d12c2b162 100644
--- a/src/journal/journalctl.c
+++ b/src/journal/journalctl.c
@@ -93,6 +93,7 @@ static bool arg_catalog = false;
 static bool arg_reverse = false;
 static int arg_journal_type = 0;
 static const char *arg_root = NULL;
+static const char *arg_machine = NULL;
 
 static enum {
         ACTION_SHOW,
@@ -120,6 +121,7 @@ static int help(void) {
                "Flags:\n"
                "     --system              Show only the system journal\n"
                "     --user                Show only the user journal for current user\n"
+               "  -M --machine=CONTAINER   Operate on local container\n"
                "     --since=DATE          Start showing entries newer or of the specified date\n"
                "     --until=DATE          Stop showing entries older or of the specified date\n"
                "  -c --cursor=CURSOR       Start showing entries from specified cursor\n"
@@ -247,6 +249,7 @@ static int parse_argv(int argc, char *argv[]) {
                 { "dump-catalog",   no_argument,       NULL, ARG_DUMP_CATALOG   },
                 { "update-catalog", no_argument,       NULL, ARG_UPDATE_CATALOG },
                 { "reverse",        no_argument,       NULL, 'r'                },
+                { "machine",        required_argument, NULL, 'M'                },
                 {}
         };
 
@@ -255,7 +258,7 @@ static int parse_argv(int argc, char *argv[]) {
         assert(argc >= 0);
         assert(argv);
 
-        while ((c = getopt_long(argc, argv, "hefo:aln::qmb::kD:p:c:u:F:xr", options, NULL)) >= 0) {
+        while ((c = getopt_long(argc, argv, "hefo:aln::qmb::kD:p:c:u:F:xrM:", options, NULL)) >= 0) {
 
                 switch (c) {
 
@@ -389,6 +392,10 @@ static int parse_argv(int argc, char *argv[]) {
                         arg_journal_type |= SD_JOURNAL_CURRENT_USER;
                         break;
 
+                case 'M':
+                        arg_machine = optarg;
+                        break;
+
                 case 'D':
                         arg_directory = optarg;
                         break;
@@ -576,8 +583,8 @@ static int parse_argv(int argc, char *argv[]) {
         if (arg_follow && !arg_no_tail && arg_lines < 0)
                 arg_lines = 10;
 
-        if (arg_directory && arg_file) {
-                log_error("Please specify either -D/--directory= or --file=, not both.");
+        if (!!arg_directory + !!arg_file + !!arg_machine > 1) {
+                log_error("Please specify either -D/--directory= or --file= or -M/--machine=, not more than one.");
                 return -EINVAL;
         }
 
@@ -881,7 +888,7 @@ static int add_boot(sd_journal *j) {
                 return 0;
 
         if (!arg_boot_descriptor)
-                return add_match_this_boot(j);
+                return add_match_this_boot(j, arg_machine);
 
         if (strlen(arg_boot_descriptor) >= 32) {
                 char tmp = arg_boot_descriptor[32];
@@ -1460,6 +1467,8 @@ int main(int argc, char *argv[]) {
                 r = sd_journal_open_directory(&j, arg_directory, arg_journal_type);
         else if (arg_file)
                 r = sd_journal_open_files(&j, (const char**) arg_file, 0);
+        else if (arg_machine)
+                r = sd_journal_open_container(&j, arg_machine, 0);
         else
                 r = sd_journal_open(&j, !arg_merge*SD_JOURNAL_LOCAL_ONLY + arg_journal_type);
         if (r < 0) {
diff --git a/src/journal/libsystemd-journal.sym b/src/journal/libsystemd-journal.sym
index 4eb15910d2..7f10f633f6 100644
--- a/src/journal/libsystemd-journal.sym
+++ b/src/journal/libsystemd-journal.sym
@@ -109,3 +109,8 @@ LIBSYSTEMD_JOURNAL_205 {
 global:
         sd_journal_open_files;
 } LIBSYSTEMD_JOURNAL_202;
+
+LIBSYSTEMD_JOURNAL_209 {
+global:
+        sd_journal_open_container;
+} LIBSYSTEMD_JOURNAL_205;
diff --git a/src/journal/sd-journal.c b/src/journal/sd-journal.c
index 2ba7ca4559..b55cf37e50 100644
--- a/src/journal/sd-journal.c
+++ b/src/journal/sd-journal.c
@@ -41,6 +41,7 @@
 #include "missing.h"
 #include "catalog.h"
 #include "replace-var.h"
+#include "fileio.h"
 
 #define JOURNAL_FILES_MAX 1024
 
@@ -1465,7 +1466,7 @@ static int add_directory(sd_journal *j, const char *prefix, const char *dirname)
         return 0;
 }
 
-static int add_root_directory(sd_journal *j, const char *p) {
+static int add_root_directory(sd_journal *j, const char *p, const char *prefix) {
         _cleanup_closedir_ DIR *d = NULL;
         Directory *m;
         int r;
@@ -1477,6 +1478,9 @@ static int add_root_directory(sd_journal *j, const char *p) {
             !path_startswith(p, "/run"))
                 return -EINVAL;
 
+        if (prefix)
+                p = strappenda(prefix, p);
+
         d = opendir(p);
         if (!d)
                 return -errno;
@@ -1576,7 +1580,7 @@ static int remove_directory(sd_journal *j, Directory *d) {
         return 0;
 }
 
-static int add_search_paths(sd_journal *j) {
+static int add_search_paths(sd_journal *j, const char *prefix) {
         int r;
         const char search_paths[] =
                 "/run/log/journal\0"
@@ -1589,7 +1593,7 @@ static int add_search_paths(sd_journal *j) {
          * what's actually accessible, and ignore the rest. */
 
         NULSTR_FOREACH(p, search_paths) {
-                r = add_root_directory(j, p);
+                r = add_root_directory(j, p, prefix);
                 if (r < 0 && r != -ENOENT) {
                         r = set_put_error(j, r);
                         if (r < 0)
@@ -1619,7 +1623,7 @@ static int add_current_paths(sd_journal *j) {
                 if (!dir)
                         return -ENOMEM;
 
-                r = add_root_directory(j, dir);
+                r = add_root_directory(j, dir, NULL);
                 if (r < 0) {
                         set_put_error(j, r);
                         return r;
@@ -1684,18 +1688,13 @@ _public_ int sd_journal_open(sd_journal **ret, int flags) {
         int r;
 
         assert_return(ret, -EINVAL);
-
-        if (flags & ~(SD_JOURNAL_LOCAL_ONLY|
-                      SD_JOURNAL_RUNTIME_ONLY|
-                      SD_JOURNAL_SYSTEM|
-                      SD_JOURNAL_CURRENT_USER))
-                return -EINVAL;
+        assert_return((flags & ~(SD_JOURNAL_LOCAL_ONLY|SD_JOURNAL_RUNTIME_ONLY|SD_JOURNAL_SYSTEM|SD_JOURNAL_CURRENT_USER)) == 0, -EINVAL);
 
         j = journal_new(flags, NULL);
         if (!j)
                 return -ENOMEM;
 
-        r = add_search_paths(j);
+        r = add_search_paths(j, NULL);
         if (r < 0)
                 goto fail;
 
@@ -1708,6 +1707,45 @@ fail:
         return r;
 }
 
+_public_ int sd_journal_open_container(sd_journal **ret, const char *machine, int flags) {
+        _cleanup_free_ char *root = NULL, *class = NULL;
+        sd_journal *j;
+        char *p;
+        int r;
+
+        assert_return(machine, -EINVAL);
+        assert_return(ret, -EINVAL);
+        assert_return((flags & ~(SD_JOURNAL_LOCAL_ONLY|SD_JOURNAL_SYSTEM)) == 0, -EINVAL);
+        assert_return(filename_is_safe(machine), -EINVAL);
+
+        p = strappenda("/run/systemd/machines/", machine);
+        r = parse_env_file(p, NEWLINE, "ROOT", &root, "CLASS", &class, NULL);
+        if (r == -ENOENT)
+                return -EHOSTDOWN;
+        if (r < 0)
+                return r;
+        if (!root)
+                return -ENODATA;
+
+        if (!streq_ptr(class, "container"))
+                return -EIO;
+
+        j = journal_new(flags, NULL);
+        if (!j)
+                return -ENOMEM;
+
+        r = add_search_paths(j, root);
+        if (r < 0)
+                goto fail;
+
+        *ret = j;
+        return 0;
+
+fail:
+        sd_journal_close(j);
+        return r;
+}
+
 _public_ int sd_journal_open_directory(sd_journal **ret, const char *path, int flags) {
         sd_journal *j;
         int r;
@@ -1720,7 +1758,7 @@ _public_ int sd_journal_open_directory(sd_journal **ret, const char *path, int f
         if (!j)
                 return -ENOMEM;
 
-        r = add_root_directory(j, path);
+        r = add_root_directory(j, path, NULL);
         if (r < 0) {
                 set_put_error(j, r);
                 goto fail;
@@ -2083,9 +2121,9 @@ _public_ int sd_journal_get_fd(sd_journal *j) {
         if (j->no_new_files)
                 r = add_current_paths(j);
         else if (j->path)
-                r = add_root_directory(j, j->path);
+                r = add_root_directory(j, j->path, NULL);
         else
-                r = add_search_paths(j);
+                r = add_search_paths(j, NULL);
         if (r < 0)
                 return r;